The live ebuild (version 9999-r1) tracking the bleeding-edge WIP codebase also remains available.

A word of warning: USE flags and keywords are to be added to portage's configuration files and every emerge operation should be executed with '-p' (short option for --pretend) appended to the command line first as per best practice!

Users of Ubuntu 14.04 LTS (Trusty) up to 15.10 (Wily) can use this PPA.